Naming Ionic Compounds

Chemical Nomenclature is the systematic naming of chemical compounds. Here we examine just a few rules for chemical substances that can be named relatively easily.

1. Name the cation (the more electropositive one) first and the anion (the more electronegative one) second.
2. Monoatomic cations take their name from the element name.
3. Monoatomic anions take their names from the first part of the element name and then add "-ide".
   
   

   Cation Name H+ Hydrogen Na+ Sodium Al3+ Aluminum

   Anion Name H- Hydride Cl- Chloride O2- Oxide

   What are the names for NaCl, MgO, and HBr?

   NaCl = sodium chloride

   MgO = magnesium oxide

   HBr = hydrogen bromide

   
   
   
   
   
4. When elements form more than one type of ionic compound Roman numerals are used to indicate the charge on the cation.

   Fe2+ and O2-	give	FeO	= Iron(II) Oxide
   Fe3+ and O2-	give	Fe2O3	= Iron(III) Oxide
   Sn2+ and Cl-	give	SnCl2	= Tin(II) Chloride
   Sn4+ and Cl-	give	SnCl4	= Tin(IV) Chloride

   There is an older system of naming these compounds that uses the Latin name of the metal with the suffices of "-ic" and "-ous" to designate the higher and lower charge of the metal, respectively.

   So the examples above would be, under the older system,

   FeO	= Ferrous Oxide
   Fe2O3	= Ferric Oxide
   SnCl2	= Stannous Chloride
   SnCl4	= Stannic Chloride

   Here are some other examples

   Ion	Latin Name	Systematic Name
   Au+	Aurous	Gold(I)
   Au3+	Auric	Gold(III)
   Cu+	Cuprous	Copper(I)
   Cu2+	Cupric	Copper(II)

   
   
   
   

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5. For polyatomic ions, you should memorize the names below.
   
   

   Ion	Name
   NH4+	ammonium
   OH-	hydroxide
   CN-	cyanide
   C2O42-	oxalate
   Cr2O72-	dichromate
   NO3-	nitrate
   SO42-	sulfate
   PO43-	phosphate
   ClO-	hypochlorite
   ClO3-	chlorate
   MnO4-	permanganate
   HSO4-	hydrogen sulfate or bisulfate
   Hg22+	Mercury(I)
   C2H3O2-	acetate
   SCN-	thiocyanate
   CrO42-	chromate
   NO2-	nitrite
   SO32-	sulfite
   CO32-	carbonate
   AsO43-	arsenate
   ClO2-	chlorite
   ClO4-	perchlorate
   HSO3-	hydrogen sulfite or bisulfite
   HCO3-	hydrogen carbonate or bicarbonate

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     Ions and Ion Names:
   • Ionic Compound Names: